Minerals have been used historically in a number of applications such as viscosifiers, anti-settling agents, thixotropes or rheological additives in both aqueous and organic systems. Numerous patents have been issued covering the uses of minerals, including smectite-type minerals, in paints, greases, cosmetics, inks, polyesters and other areas. Also it has been known for many years that layered silicate minerals such as kaolinite, mica, vermiculite, and smectites have a natural exchange capacity for cationic compounds both of the inorganic and organic types. It is this natural exchange capacity characteristic which allows smectitic clays to be converted to useful thixotropes for organic systems. Also it has been known for many years that an organic cationic dye, such as methylene blue, could be used to obtain an approximate measure of the cationic exchange capacity of such minerals. In this procedure the cationic organic dye is exchanged onto the clay surface. It has also been known that organic cationic dyes can be fixed to any layered silicate mineral that possessed an ionic charge.
The pigment to be dyed must accept and hold the dye, not only during the dyeing step but also in subsequent processing steps. Failure to hold the dye results in reduced efficiency of the treatment, and disposal or recirculation of colored filtrates is economically undesirable.
The prior art is aware of products which are coloring agents in printing inks. For example, U.S. Pat. No. 4,410,364, discloses a printing ink formed by dispersing therein an ink coloring material and an organophilic clay gellant. In this patent, the organophilic clay gellant is the reaction product of an organic cation, an organic anion, and a smectite-type clay which has a cationic exchange capacity of at least 75 milliequivalents per 100 grams of the clay so that an organic cation-organic anion complex is intercalated with the smectite-type clay and the cationic exchange sites of the smectite-type clay are substituted with the organic cation.
A series of earlier patents disclose thixotropes or rheological agents by reaction of various clay minerals and cationic agents. However, these products are not coloring agents. Thus, U.S. Pat. No. 4,116,866 discloses the reaction product of a clay with a quaternary ammonium cationic compound. Of the clays disclosed in this patent, there is mentioned bentonite and hectorite, the latter being described as a swelling magnesium-lithium silicate clay. Other types of smectite-type clays disclosed in this patent for reaction include montmorillonite, beidellite, saponite and stevensite. A similar product is disclosed in U.S. Pat. No. 4,287,086.
U.S. Pat. Nos. 4,216,135 and 4,081,496 to Finlayson disclose organophilic clays and thixotropic polyester compositions which contain these clays. This product is the reaction product of a smectite-type clay with a methybenzyl dialkyl ammonium compound, or a dibenzl dialkyl ammonium compound. The products are said to be dispersable in organic liquids to form gels and the gels may be added as gelling agents to polyester compositions.
U.S. Pat. No. 4,105,578 to Finlayson et al discloses organophilic clay gellants prepared as the reaction product of a smectite-type clay and a quaternary ammonium compound. These products are also said to have good dispersability in organic liquids and to form gels and to be useful in lubricating greases, oil paste muds, oil-based packer fluids, paint-varnish-lacquer removers, paints, and foundry molding sand binders and the like.
A series of older U.S. patents including U.S. Pat. Nos. 2,531,440, 2,531,427, and 2,966,506 disclose modified clay complexes which are compatible with organic liquids. These organic clay complexes comprise the reaction product of a clay such as montmorillonite or bentonite and including hectorite with an organic compound of the quaternary ammonium type. The clays used in this series of patents are said to have base exchange capacities which range from about 15 to 100 based on milliequivalents of exchangeable base per 100 grams of clay. These products are disclosed for use as gelling agents.
U.S. Pat. No. 4,382,868 discloses organophilic clays which have enhanced dispersability in organic liquids, the organophilic clays being prepared by extruding a mixture of a smectite clay, a quaternary cationic organic compound, water and an alcohol. U.S. Pat. No. 3,974,125 discloses thixotropic agents comprising clays which have been reacted with dialkyl dimethyl ammonium quaternary salts and incorporation of these products into polyesters. U.S. Pat. No. 3,864,294 discloses coating compositions in the form of a gel which comprise an amine modified montmorillonite clay, a swelling agent therefor, and a non-volatile oleaginous agent for wetting the clay. This product is indicated as adapted for pigment-containing coating systems such as in nail enamel compositions.
Published and unexamined Japanese patent application (Kokai) No. 50-72,926 published Jun. 16, 1975, discloses a method of manufacturing pigments which contain organic coloring agents. These pigments are produced by dispersing a mineral which has clay properties and ionic exchange capabilities in water. To this slurry is added an aqueous solution of an organic coloring element to effect chemical bonding and render the resulting product insoluble in water from which it may be recovered. The clays disclosed for use in this patent include montmorillonite, zeolites and bentonite. The coloring agents are primarily organic dyes.
European Patent Application No. 206,800, published Mar. 30, 1986, discloses water insoluble pigments which comprise a complex of the water insoluble inorganic anionic exchange material which has a layered structure and a water soluble dye. The anionic exchange material with the layered structure may comprise any of a number of known mineral materials including magnesium aluminum chloride and the dyes are organic dyes.
The present invention provides a coloring pigment useful for coloring materials which is an improvement over these prior known products.